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221.
222.
N. R. Sibgatullin 《Astronomy Letters》2001,27(12):799-808
The inclination of low-eccentricity orbits is shown to significantly affect orbital parameters, in particular, the Keplerian, nodal precession, and periastron rotation frequencies, which are interpreted in terms of observable quantities. For the nodal precession and periastron rotation frequencies of low-eccentricity orbits in a Kerr field, we derive a Taylor expansion in terms of the Kerr parameter at arbitrary orbital inclinations to the black-hole spin axis and at arbitrary radial coordinates. The particle radius, energy, and angular momentum in the marginally stable circular orbits are calculated as functions of the Kerr parameter j and parameter s in the form of Taylor expansions in terms of j to within O[j 6]. By analyzing our numerical results, we give compact approximation formulas for the nodal precession frequency of the marginally stable circular orbits at various s in the entire range of the Kerr parameter. 相似文献
223.
Alessandro Marconi Roberto Maiolino Romain G. Petrov 《Astrophysics and Space Science》2003,286(1-2):245-254
Interferometry in the optical and near infrared has so far played a marginal role in Extragalactic Astronomy. Active Galactic
Nuclei are the brightest and most compact extragalactic sources, nonetheless only a very limited number could be studied with
speckle interferometry and none with long baseline interferometry. The VLTI will allow the study of moderately faint extragalactic
objects with very high spatial resolution thus opening a new window on the universe. With this paper we focus on three scientific
cases to show how AMBER and MIDI can be used to tackle open issues in extragalactic astronomy.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
224.
225.
A Fundamental Plane of black hole activity 总被引:1,自引:0,他引:1
226.
227.
Measurements of Iapetus as seen at 20 and 2.2 μm in the shadow of Saturn's ring are given, providing the thermal response to a rapidly varying heat input. The 20 μm thermal emission follows the 2.2 μm flux input closely. The observations, plus a simple diffusion calculation, imply that the surface of Iapetus is made of material having a very small thermal inertia, probably . 相似文献
228.
Yu. P. Ilyasov M. Imae Y. Hanado V. V. Oreshko V. A. Potapov A. E. Rodin M. Sekido 《Astronomy Letters》2005,31(1):30-36
We present the results from our timing of the millisecond pulsar B1937+21, performed jointly since 1997 on two radio telescopes: the RT-64 in Kalyazin (Russia) at a frequency of 0.6GHz and RT-34 in Kashima (Japan) at a frequency of 2.15 GHz. The rms value of the pulse time of arrival (TOA) residuals for the pulsar at the barycenter of the Solar system is 1.8 μs (the relative variation is ≈10?14 over the observing period). The TOA residuals are shown to be dominated by white phase noise, which allows this pulsar to be used as an independent time scale keeper. The upper limit for the gravitational background energy density Ωgh2 at frequencies ≈6.5 × 10?9 Hz is estimated to be no higher than 10?6. Based on the long-term timing of the pulsar, we have improved its parameters and accurately determined the dispersion measure and its time variation over the period 1984–2002, which was, on average, ?0.00114(3) pc cm?3 yr?1. 相似文献
229.
R. V. Shcherbakov 《Astronomy Letters》2005,31(9):591-597
We investigate the properties of an axisymmetric gas flow without angular momentum onto a small compact object, in particular, on a Schwarzschild black hole in the supersonic region; the velocity of the object itself is assumed to be low compared to the speed of sound at infinity. First of all, we show that the streamlines intersect (i.e., a caustic is formed) on the symmetry axis at a certain distance r x from the center on the front side if the pressure is ignored. The characteristic radial size of the region in which the streamlines emerging from the sonic surface at an angle no larger than θ0 to the axis intersect is Δr = r x θ 0 2 /3. To refine the flow structure in this region, we have numerically computed the system without ignoring the pressure in the adiabatic approximation. We have estimated the parameters of the inferred region with anomalously high matter temperature and density accompanied by anomalously high energy release. 相似文献
230.
In this paper we give a detailed general relativistic formulation of the study of structure and stability of charged fluid
disks around compact objects like black holes neglecting the self-gravitation of the disk itself. Having presented the general
equations for equilibrium as well as for perturbations we solve explicitly the cases of rigidly and differentially rotating
thin disks, with constant charge density and zero pressure, confined to the equatorial plane of the black hole. By using normal
mode analysis we have analysed the stability of such disks under purely radial perturbations and find that the disks are generally
stable.
On leave of absence from Government College, Jagadalpur 494005 相似文献